Flexible hose of the type commonly used for vacuum cleaners has been constructed of an outer wall of helically wrapped plastic strip, a self-supporting helical reinforcing element inside the outer wall and often a plastic liner inside the reinforcing element. The reinforcing element has typically been of composite form comprising an inner metal round wire about which a cylindrical plastic sheath is extruded, so that the plastic sheath can be bonded to both the outer wall of the hose and to the liner. The hose structure is usually formed on a mandrel with the plastic strips for the wall and liner extruded as they are applied. These plastic elements are therefore initially soft and somewhat deformable.
Because of the circular cross-section of the reinforcing element it has a tendency to penetrate into and at times through the soft plastic inner ply. This penetration has been the cause of a relatively high product rejection rate. Also there is a small gap or delamination region on both sides of the wire due to its round cross-sectional shape. When the hose is flexed or bent at right angles the liner at these delaminated areas tends to convolute inwardly on the inside of the hose and thus cause air friction loss and air turbulence.